This invention relates to an electrostatic chuck and more particularly to an improved electrostatic chuck for securing a work by electrostatic forces in a vacuum process apparatus such as a dry-etching apparatus.
In a vacuum microfabrication apparatus such as a dry-etching apparatus, a variety of means for securing a wafer have been used. In recent years electrostatic chucks are used for securing a specimen wafer by electrostatic forces.
Japanese Patent Laid-Open Publication No. 85828/1981 discloses an electrostatic chuck of a type which has a holding portion for holding a wafer. The holding portion is so formed that its size is almost the same as that of a wafer to be processed. The holding portion comprises a first insulator layer, a plurality of electrodes provided upon the first insulator layer, and a second insulator layer provided upon the plurality of electrodes and over the first insulator layer. The other portion except the holding portion consists of a metal support body such as a stainless steel member.
In operation, the specimen wafer is placed over the holding portion of the electrostatic chuck. When a high voltage is applied to the electrodes, the electrostatic attractive forces arise and attract and securely hold the specimen wafer in position. A vacuum process such as etching is done thereafter.
The above described electrostatic chuck can prevent wear and degradation of the second insulator layer contacting directly the wafer since the holding portion is entirely covered by the specimen wafer. However, though the insulator layer is protected from wearing, the upper surface of the metal support body is subjected to an etching process, with a result that the metallic material of the support body may disperse or scatter as impurities.
In addition, although a high temperature during the etching process often has an adverse effect on the wafer, no consideration has been made to mitigate heat impacts regarding the electrostatic chuck.